This calls for the Strawberries to be added during primary fermentation. But most of the experts in blind tests have preferred meads with fruit (actually called Melomel's) added during secondary. If those words are gibberish to you, primary means the initial fermentation. Usually this is between 1 week and 4 weeks. However long it takes for the yeast to get an ABV up to about where you want it (anywhere between 11%-14%). The Strawberry-Banana Mead in the picture above went from 0-14.3% in a week. I also have another mead going that is only at 4%, and it's been 2 weeks. So the time it takes can vary. Once the fermentation has petered out, you rack (removing of the juice) off the lees (all that stuff sitting on the bottom of the carboy). You usually put this in another carboy, or in a temporary sanitized bucket while you clean out the first one, and back into the original. This is now called your secondary vessel.
The only reason I added the fruit during primary rather than secondary, is I learned to make it during primary and it always came out good. So I have no good reason to change up the recipe. But feel free do add the strawberries after the primary fermentation is done.